aha.. once again another person who was sucked into the compaq presario sr series.. haha, i too was one of them.. and you don't need an utterly astonishly expensive graphics card to play fear, my gs runs it 1024x768 with 2xAA 4xAniso and averages out 55 fps, which is very playable to me... havent tried playing without the 2, but i'm betting its higher... ya, i had the compaq sr1650nx
as for the psu, i called compaq to make sure it was a 350 watt.. and it was, but i think maximum wattage it will put it is 320, i think it said that on the label of the psu, if my model has the same psu as your's... but definitely going to need a new one, i don't know how long a beefy graphics card would last with that one...